Question for the Whacker guys

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Becket

New member
I am running a 10 1/2 X 12p four blade prop on our flat bottom river boat, It's a Yamaha 40, we are looking for a little more top end and we put a three blade 10 1/2 X 14p on it and it changed NOTHING, It still runs 36 mph and the rpms are the same, my question is, Should I try a four blade 10 1/2 X14p? What is the better of the two, 3 or 4 blade?  Pros/cons? :smile21:
 

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Crusader

Crusader

Moderator
What is the recommended WOT Rpm range??? You'd have to get a prop that will allow the motor wind run in the mfgrs WOT RPM range and accept the top end speed you get from that.

There are formulas out there that can help you determine the slippage etc. there's so much more to a modern prop nowadays than just the pitch.
 
S

scarabscs

New member
A three blade prop will give better speed than a 4 blade, but will not cruise as good.  A 4 blad will have better cruise speed, but the 4th blade will cause more drag at high speed and will hurt your top end a bit.

I would look at getting a stainless 3 blade for it, your gonna spend some $$ but you might pick up a few mph.

Check out the quicksilver Merc Props, and the Michigan wheel props.  They both sell stainless that will fit your motor.

Other option is http://www.summitracing.com/parts/NOS-05029NOS/  :smile16:
 
B

Becket

New member
Sounds like the 4 Blade would handle a load better at cruise and get us on plane faster with a heavy load, The boat is often loaded heavy While we are running lines so if I am thinking correctly we should stay with a 4 Blade and maybe step up a couple pitches for use like that but then A 3 blade with a little more bite would be best when we are just Riding. Am I on the right track? When we fish in Gorda we put lots of miles behind us with a light load so that is where we are looking for more top end and the 3 Blade would do good there.  think.gif

The NOS is a grand Idea but I don't want to tie everything down in the Boat!  crazy.gif
 
B

Becket

New member
soldier of fortune said:
trust me i am a outboard owner too i know things
Click to expand...
10-4, as a mechanic I have rebuilt more of them than I can count, I do all the mechanic work for lago vista lodge, they have 30 boats for clients that more often than not have NO idea how to run a boat! they can do some strange things to an engine! they are running Merc and Suz. 60hp four strokes.

As you can tell we have put a little bigger Engine on this boat than its rated for but we needed the power, I have just never experimented with props too much and at a 100+ bux a pop I dont want to do alot of guess work!
 
Crusader

Crusader

Moderator
I'm running a three blade SS 13p prop on the 13' Whaler with a 40hp Yammy.

Whlr_texoma_lbr_day_2009-1.jpg
 
B

Becket

New member
Crusader said:
I'm running a three blade SS 13p prop on the 13' Whaler with a 40hp Yammy.

Whlr_texoma_lbr_day_2009-1.jpg
Click to expand...
Ours runs good with the 3 or 4 blade but what has me puzzled is why there was absolutly no change? I would have thought the SS 3b 14p would have give more top end but nothing changed execpt that it was a little slower out of the hole? It will almost jump comleatly out of the water with the 4 Blade and it takes about two full lenghths to plane with the 3 blade but both only run it to 36mph with no change in rpm? the Engine is running in the right WOT rpms, no strain or over rev. with either prop.
 
Crusader

Crusader

Moderator
Here's whats going on. As I've stated earlier, props are different animals now than they were just a few short years ago. The four bladed prop, though it looks sexier, is basically used to pop the boat up and out of the water a little more quickly and because of the blade design, will provide more stern lift than the three bladed prop. I've found that people invest in a four blade because it looks cool however they are disappointed that the boat doesn't really provide and added top end speed.

Here's a website with a tutorial that can help with a basic understanding of how a prop works and I've used it to broaden my understanding of them.

http://www.dansdiscountprops.com/propeller_basics.cfm

This website actually talks about the differences between a 3 and 4 bladed prop and when to use each.

http://www.propmd.com/t-propellerbasics.aspx

http://alansorum.suite101.com/boat-propeller-basics-a34305


 
Crusader

Crusader

Moderator
Gas-Hole said:
Crusader said:
I'm running a three blade SS 13p prop on the 13' Whaler with a 40hp Yammy.

Whlr_texoma_lbr_day_2009-1.jpg
Click to expand...
Ours runs good with the 3 or 4 blade but what has me puzzled is why there was absolutly no change? I would have thought the SS 3b 14p would have give more top end but nothing changed execpt that it was a little slower out of the hole? It will almost jump comleatly out of the water with the 4 Blade and it takes about two full lenghths to plane with the 3 blade but both only run it to 36mph with no change in rpm? the Engine is running in the right WOT rpms, no strain or over rev. with either prop.
Click to expand...

If you're operating in the WOT range, I'm afraid that 36MPH is about all you're going to get out of her.
 
B

Becket

New member
Crusader said:
Here's whats going on. As I've stated earlier, props are different animals now than they were just a few short years ago. The four bladed prop, though it looks sexier, is basically used to pop the boat up and out of the water a little more quickly and because of the blade design, will provide more stern lift than the three bladed prop. I've found that people invest in a four blade because it looks cool however they are disappointed that the boat doesn't really provide and added top end speed.

Here's a website with a tutorial that can help with a basic understanding of how a prop works and I've used it to broaden my understanding of them.

http://www.dansdiscountprops.com/propeller_basics.cfm

This website actually talks about the differences between a 3 and 4 bladed prop and when to use each.

http://www.propmd.com/t-propellerbasics.aspx

http://alansorum.suite101.com/boat-propeller-basics-a34305
Click to expand...
Cool, Thanks for the Info, I will check this out, Never hurts to learn new stuff.
 
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